This circuit is from a 1982 publication but can be assembled with BF245 for Q1 and BC548 for Q2. The crystal headset can be replaced with a ceramic capsule. The circuit has a gain selector switch and is powered by a 9 V battery.
This circuit is from a 1982 publication but can be assembled with BF245 for Q1 and BC548 for Q2. The crystal headset can be replaced with a ceramic capsule. The circuit has a gain selector switch and is powered by a 9 V battery.